01 May 08

Scientists from Oxford University have, for the first time, shown how chemical reactions could enable birds to navigate by the Earth’s magnetic field.

Birds, mammals, reptiles, insects and many other species are known to use the Earth’s magnetic field to find their way around. But, while various mechanisms have been suggested to explain this ability, until now no one has demonstrated how these could detect and use such a weak magnetic field. 

‘Because the Earth’s magnetic field is so weak many people found it difficult to understand how it could affect bird or animal sense organs in a way which would help them to navigate,’ said Professor Peter Hore of Oxford University’s Department of Chemistry who, with Dr Christiane Timmel, led the research: they report their findings in this week’s Nature.

‘Our experiments with a model chemical system prove that it is possible for molecules to detect weak magnetic fields and to respond to their directions.’ 

In the model system the weak magnetic field interacts with electron spins in radical pair reaction intermediates, changing their lifetimes. While the molecule used to produce the ‘radical pairs’ is not the basis of a bird’s ‘chemical compass’ it demonstrates how such a compass could work.

‘Birds may use similar chemical reactions in their retinas, where photochemical reactions could lead to nerve signals which help them to orient,’ comments Professor Hore. ‘Over millions of years birds, and other animals, have evolved exquisitely sensitive chemical compasses which we are only beginning to understand. Our work outlines the principles behind such a compass; we hope that biochemists and neurophysiologists will be able to identify and locate the molecules involved and elucidate the biochemical signalling pathways.’ 

The research was principally supported by the Engineering and Physical Sciences Research Council (EPSRC), the Human Frontier Science Program and the EMF Biological Research Trust.